I am trying to plan which fish I am going to have in my 55 gallon aquarium and I think I am making it harder than it needs to be. This is what I know about my water parameters - GH and KH are 79 ppm which equates to 4dH. My pH out of the tap is 7.6. So my understanding thanks to Byron is that I have soft, slightly basic water.

All that being said, I can't decide which fish would be suitable for my tank without tweaking the water. One website says tiger barbs need a pH of 6-7 while another says they need a pH of 6.5-7.5.

I also like the tetras esp. the Cardinals, but on one website says pH of 5.5-7.5 and another says 4.5-7. I would love to have some tetras, but I don't know if they will survive long term with my water.

Can anyone help me sort this out? Everything I have read seems to have contradictions on other sites.

Hi SusanB. Well there are very mixed opinions on this. One is that if you force a fish to live in the wrong PH it stresses the fish over time and will shorten their life span. So I with a PH of 8.2 would never consider purchasing and housing Discus that like acidic water which is below 7. I should buy African Cichlids and live bearers.
The flip side, if they are housed in "my town, at the LFS" then they should thrive in my same PH water, both being 8.2. And the Discus are on display right there at the LFS in the Basic water. Should be good. Hmmmmmmm. I believe in the first option.
I know that adding chemicals to your tank... PH UP and PH down is really dangerous to your fish. I can't explain it I'm afraid, just that water has a way of finding is way back to it's natural ph balance and the swing can kill your fish. And I also know that you can add natural things, rock, types of wood that will cause smaller more steady changes.
Whatever you decide to buy, make sure you acclimate the new fish with a trickle of tank water into the bag every 5 minutes (or the drip method) so that you at least double the volume of the bag by the time you have matched the temperature of your tank's water.
If the PH is really close... say off by .5 I would not even think twice about it.
Good luck.

Hi SusanB. Well there are very mixed opinions on this. One is that if you force a fish to live in the wrong PH it stresses the fish over time and will shorten their life span. So I with a PH of 8.2 would never consider purchasing and housing Discus that like acidic water which is below 7. I should buy African Cichlids and live bearers.
The flip side, if they are housed in "my town, at the LFS" then they should thrive in my same PH water, both being 8.2. And the Discus are on display right there at the LFS in the Basic water. Should be good. Hmmmmmmm. I believe in the first option.
I know that adding chemicals to your tank... PH UP and PH down is really dangerous to your fish. I can't explain it I'm afraid, just that water has a way of finding is way back to it's natural ph balance and the swing can kill your fish. And I also know that you can add natural things, rock, types of wood that will cause smaller more steady changes.
Whatever you decide to buy, make sure you acclimate the new fish with a trickle of tank water into the bag every 5 minutes (or the drip method) so that you at least double the volume of the bag by the time you have matched the temperature of your tank's water.
If the PH is really close... say off by .5 I would not even think twice about it.
Good luck.

It is all so very confusing. I think I believe in the first option as well. I am about five minutes from the LFS which uses the same water supply that I do and they are of the opinion that if it works in their water it should work in mine. That may be a true statement short term, but they sell their fish pretty quickly I'm not sure they know the long term effects of what their water parameters can do to the fish.

I think the best situation for my tank may be a species tank of Tiger barbs. My water is so weird, it seems as if the fish who do well in soft water need a low pH and fish that need hard water prefer a high pH. It is not so easy to find anything that can tolerate soft water with a 7.6 pH.

First, pH is closely connected to the GH/KH, and the GH is actually more significant on fish.
Second, some fish can adjust to a certain extent, some fish cannot; or if they do, it is short-term.
Third, the fact that any fish is alive in the store tank for the limited time it is there does not mean the fish is not experiencing stress from their water, and will in yours too.

A comment on the pH ranges, yes, you will find variation with this as with almost any aspect of this hobby. One has to consider the source of the information in order to determine its reliability, and these days, anyone can set up a web site and say whatever with no actual knowledge behind it.

We have fish profiles here, and the ranges for water parameters (GH, pH and temperature) are reliable because they are the consensus of knowledgeable ichthyologists and experienced hobbyists. I wrote most of the profiles, and if i ever find a contradictory value from a reliable source, I mention it so one has all the facts.

To your case, you will have no trouble with any soft water fish, perhaps with a few exceptions and those being wild caught. The pH will tend to lower, and with your GH (and presumably low KH) I would expect your tanks to run just below 7 when they are established.

Final comment on short-term adjustment of fish to parameters outside their preference. These fish usually die sooner, i.e., they do not live to their normal lifespan. For example, cardinal tetra rarely live more than 3-5 years when kept in anything other than very soft water; in soft water, they can live more than 10 years. During the four or five years in harder water, everything appears fine. But the fish will die. Usually it is calcium blockage in the kidneys, something you cannot see without dissection after death. I wrote more on this in a recent thread. But the point is, that all fish evolved naturally to live in very specific water parameters, and it is simply not feasible that we are going to change thousands of years of natural evolution just because we may want to.

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.[unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]

Alrighty then, I think I will change my original idea from tiger barbs to a school of flame tetras and a school of glowlight tetras. I wasn't in love with the idea of tiger barbs because they are semi-aggressive, but it was the only thing I could find that seem to match my parameters the best. Knowing that the gH is more important helps in opening up the choices.

Alrighty then, I think I will change my original idea from tiger barbs to a school of flame tetras and a school of glowlight tetras. I wasn't in love with the idea of tiger barbs because they are semi-aggressive, but it was the only thing I could find that seem to match my parameters the best. Knowing that the gH is more important helps in opening up the choices.

Thanks again!

This sounds fine. Almost any of the characins will manage in your water.

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.[unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]